Why do I need to check suspension?
If simple, a suspension is the part of your vehicle that holds the wheels and, obviously, any suspension defect can make a car unsafe to drive. For example, if such a small thing as a tie rod end will accidentally disjoint (which exactly happened with the one in the picture) the vehicle will immediately loose the steering control.
Obviously, the only way to check the car is to have it inspected by professional mechanic. This guide is not intended to substitute an inspection by a mechanic. In order to help you keeping your car safe, I wrote down few simple tips that may help you to discover a possible problem with your car on early stage. So you'll be able to have your vehicle inspected before it cause something serious.
• At the beginning
• Check shock absorbers (struts)
• Check the steering
• Check visible bushings
• Check the tires wear
• Test drive
• Have the car inspected by a mechanic
At the beginning
Look at the car from the distance, does it sit level? Does the car sit too low? (except when the vehicle has lovered suspension)
Any of these indicate some suspension wear or defect. Real life example: A recall was issued on certain models of Ford Contour regarding broken front coil spring. If your Ford Contour sits much lower than when it was new, chances are high that you face exactly this problem and you may wish to visit your local Ford dealer to have your car inspected.
Check front and rear shock absorbers (struts)
First, have a look. The shock absorbers should be dry, and the shock's boots (covers) should not be damaged. Look at this image. This is Mercedes-Benz' front shock absorber. It looks good and its boot is in good shape. Check all the four shocks (struts) this way
Look at this strut on this image. The oil starts leaking out from the strut (shock absorber) and its boot is broken. Which means the oil is coming out of the shock absorber and in a very short time (if not yet) it will stop working, making your car unsafe to drive. If the shock absorber is leaknig, it must be replaced - visit your dealer (mechanic).
If all the four shock absorbers look good, try to test their work. Try to push down every one of four vehicle's corner one by one. The car should get down easy and then get up smoothly and slowly if the corner's shock is OK. The vehicle should not bounce up and down more than 1 - 2 time. The more bouncing, the worse condition of the shock absorber.
Check visible bushings.
If it's possible, try to check visible part of suspension such as bushings (pointed with arrows in the picture), ball joints, steering linkages, etc. If you see any damage, cracks, broken boots or whatever seems improper, have your car inspected by a mechanic - it probably needs some job done.
Check the steering.
Try to shake quickly steering wheel turning it left and right at a small degree (quarter of full circle) . There should not be excessive free play, neither knocking noises. If the car has the power steering, try to do so with the engine running. Check the power steering for a leaks. Check steering fluid level. If you find any leaks, have your car inspected by a mechanic - if the power steering starts leaking, it will stop working soon. If the car has rack & pinion type steering mechanism (as in the image), try to check both of steering boots (marked with an arrow) they should not be damaged. If any of them has some damage, it hast to be replaced - have your car inspected.
Check the tires wear
If any of the tires has irregular wear (look at the image, the tire is almost bald outside) it's a sign of improper alignment, or a suspension defect. Improper wheel alignment make the car unsafe to drive at high speed. Have the car inspected.
Test drive
Best way to check the suspension - on a test drive. Turn off the radio, heater, close all windows during a test and listen for noises. Make sure, the noise isn't coming from something left in the glove box or in the trunk. Try to drive on a rough road. Any noise (e.g knocking, thumping, clicking) coming out from suspension indicates a problem. The car should hold the road well and not bounce like boat. The steering should not be difficult. The car shouldn't pull aside. If any of these conditions presents, there is some possible problem
Mechanical inspection
As a last step prior buying a used car, have the vehicle inspected by an experienced mechanic of your choice